Hi all,

We want to implement the MBED in a 3V3 application.

Only PWM output is used in the application.

Can the MBED be run on 3V3 only.

Does it need any modifications?

Thanks,

Hans

It looks like the mbed needs at least 4.5V on the Vin pin. If you only have a 3.3V power supply then you could solder a wire to the 3.3V node (large tab of the voltage regulator near the Vin pin “LD33”), but the I/O is always 3.3V.

Ben

Ben, Thx for the tip.

I will try and report if it works. It is a battery (lipo a123) feeded application and i will try to lower the voltage to a save bottom. My experience with other chips is that 3V1 mostly functions. The reason to lower the voltage to a minimum is to lower the current.

Hi Marchel,

We are trying to do a similar thing powering the mbed from at 3.7 volt Lipo battery - regulating the voltage to 3.3v and then feeding that into the two voltage regulators on the mbed. We did a quick test connecting 3.3v to the large tab on the two voltage regulators and that works fine.

I am wondering though whether it is safe to plug the mbed into the usb port while it is connected to the lipo battery? Did you have any experience with that?

/lars

Lars -

When the mbed is connected via USB, the 5-volt USB supply powers the on-board 3.3v regulators. That could possibly cause a "charging current" to flow from the powered-up regulator back into your battery - which might or might not be a good thing.

However, since you are using your own regulator to drop the 3.7v battery down to 3.3v, perhaps the reverse current path is blocked by that regulator.

Or you could just use a BAT-60 low-forward-voltage-drop diode in series with the raw battery before connecting it to the mbed regulator tab. That would simultaneously drop the battery voltage a bit and prevent reverse current. You might need two devices in series to get down to 3.3v.